POST UPDATED IN October, 2021
The ECT sensor is a sensor of the NTC (Negative Temperature Coefficient) type, and basically indicates that the resistance of the sensor falls when the temperature rises. This sensor is located in the thermostat housing or as it is also known, water intake. The Engine Coolant Temperature sensor uses a thermistor and the resistance of this varies according to the temperature.
When the resistance of the ECT sensor falls, the temperature rises and when the resistance rises, the temperature drops. The output voltage acts according to the temperature of the refrigerant, which is connected in series, through a resistance of 5 volts of the ECM (Engine Control module) that is delivered to the sensor ECT (Engine Coolant Temperature).
Its function is to inform the ECM (Engine Control module) so that it calculates the fuel delivery, the time synchronization and the control of the EGR valve (Exhaust Gas Recirculation), in the same way to activate or deactivate the radiator fan. This signal, because it is not linear, is delivered to the Engine Control Module (ECM) so that it becomes an indication of the coolant temperature. When the engine is cold, the ECM multiplies the fuel injection time as well as the ignition duration, based on the coolant temperature information, with the aim of not shutting down the engine.
In the event that the engine coolant temperature signal is lower than the minimum range for normal operation, the Check Engine light is illuminated on the board.